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16 pages, 5644 KiB

Open AccessArticle

Collaborative Effect of In-Plasma Catalysis with Sequential Na₂SO₃ Wet Scrubbing on Co-Elimination of NOx and VOCs from Simulated Sinter Flue Gas

by Juexiu Li, Rui Zhao, Maiqi Sun, Qixu Shi, Mingzhu Zhao, Junmei Zhang, Yue Liu and Jinping Jia

Processes 2023, 11(10), 2916; https://doi.org/10.3390/pr11102916 - 05 Oct 2023

Viewed by 787

Abstract

Sinter flue gas produced by the iron-ore sinter process in steel plants is characterized by a large gas volume and complex components. Among the major air pollutants, preliminary emissions of volatile organic compounds (VOCs) and nitrogen oxides (NOx) exhibit an inevitable contribution to [...] Read more.

Sinter flue gas produced by the iron-ore sinter process in steel plants is characterized by a large gas volume and complex components. Among the major air pollutants, preliminary emissions of volatile organic compounds (VOCs) and nitrogen oxides (NOx) exhibit an inevitable contribution to secondary aerosol and ozone formation. Herein, oxidation–absorption collaborative technology for in-plasma catalysis with sequential Na₂SO₃ wet scrubbing, aiming at co-elimination of NOx and VOCs from sinter flue gas, is proposed. Experimental parameters, including plasma discharge status, NO initial concentration, gas feed flux, Na₂SO₃ concentration, pH value, and absorption ions, were systematically investigated. The VOC and NOx removal performance of the integrated system was further investigated by taking simulated sinter flue gas as model pollutants. The results showed that the collaborative system has satisfactory performance for TVOC and NO removal rates for the effective oxidation of in-plasma catalysis and Na₂SO₃ absorption. The integration of plasma catalysis with Na₂SO₃ scrubbing could be an alternative technology for the co-elimination of sinter flue gas multi-compounds. Full article

(This article belongs to the Special Issue Environmental Catalysis and Air Pollution Control)

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14 pages, 4276 KiB

Open AccessFeature PaperArticle

The Promoting Effect of Metal Vacancy on CoAl Hydrotalcite-Derived Oxides for the Catalytic Oxidation of Formaldehyde

by Yimeng Chen, Shunzheng Zhao, Fengyu Gao, Qingjun Yu, Yuansong Zhou, Xiaolong Tang and Honghong Yi

Processes 2023, 11(7), 2154; https://doi.org/10.3390/pr11072154 - 19 Jul 2023

Viewed by 844

Abstract

Formaldehyde (HCHO) is a major harmful volatile organic compound (VOC) that is particularly detrimental to human health indoors. Therefore, effectively eliminating formaldehyde is of paramount importance to ensure indoor air quality. In this study, CoAl hydrotalcite (LDH) was prepared using the co-precipitation method [...] Read more.

Formaldehyde (HCHO) is a major harmful volatile organic compound (VOC) that is particularly detrimental to human health indoors. Therefore, effectively eliminating formaldehyde is of paramount importance to ensure indoor air quality. In this study, CoAl hydrotalcite (LDH) was prepared using the co-precipitation method and transformed into composite metal oxides (LDO) through calcination. Additionally, a metal Al vacancy was constructed on the surface of the composite metal oxides (E_X-LDO and E_X-LDO/NF) using an alkaline etching technique. SEM demonstrated the successful loading of CoAl-LDO onto nickel foam surfaces (LDO/NF), and an extended etching time resulted in a greater number of porous structures in the samples. XRD confirmed the successful synthesis of the precursor materials, CoAl hydrotalcite (CoAl-LDH) and CoAl layered double oxides (CoAl-LDO). EDS analysis confirmed a reduction in aluminum content after alkaline etching. XPS analysis verified the presence of abundant Co²⁺ and surface oxygen as crucial factors contributing to the catalyst’s excellent catalytic activity. The experimental results indicated that catalysts containing metal cation vacancies exhibited superior catalytic performance in formaldehyde oxidation compared to conventional hydrotalcite-derived composite oxides. H₂-TPR confirmed a significant enhancement in the participation of lattice oxygen in the catalytic oxidation reaction; it was found that the proportion of surface lattice oxygen consumption by the E₅-LDO catalyst (30.2%) is higher than that of the LDO catalyst (23.4%), and the proportion of surface lattice oxygen consumption by the E₁-LDO/NF catalyst (27.5%) is higher than that of the LDO/NF catalyst (14.6%), suggesting that cation vacancies can activate the surface lattice oxygen of the material, thereby facilitating improved catalytic activity. This study not only reveals the critical role of surface lattice oxygen in catalytic oxidation activity, but also aids in the further development of novel catalysts for efficient room-temperature oxidation of HCHO. Moreover, it provides possibilities for developing high-performance catalysts through surface modification. Full article

(This article belongs to the Special Issue Environmental Catalysis and Air Pollution Control)

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13 pages, 3301 KiB

Open AccessArticle

To Promote the Catalytic Ozonation of Typical VOCs by Modifying NiO with Cetyltrimethylammonium Bromide

by Chenguang An, Xinxin Jiang, Wei Hong, Ye Sun and Tianle Zhu

Processes 2023, 11(7), 1893; https://doi.org/10.3390/pr11071893 - 23 Jun 2023

Viewed by 740

Abstract

A series of mesoporous NiO catalysts with high specific surface area were prepared by a simple hydrothermal method and modified by cetyltrimethylammonium bromide (CTAB) as the crystal structure directing regent. The characterization with SEM, XRD, BET, and H₂-TPR results demonstrated that [...] Read more.

A series of mesoporous NiO catalysts with high specific surface area were prepared by a simple hydrothermal method and modified by cetyltrimethylammonium bromide (CTAB) as the crystal structure directing regent. The characterization with SEM, XRD, BET, and H₂-TPR results demonstrated that the introduction of CTAB effectively improved the dispersion, specific surface area, and pore volume and redox ability of NiO, and thus exposed more active sites. Meanwhile, the NiO catalyst with a CTAB/NiSO₄·6H₂O molar ratio of 2/3 exhibited the better catalytic ozonation performance of toluene, formaldehyde, methanol, and ethyl acetate than NiO. The in-situ DRIFTS elucidated the reaction path of catalytic ozonation of toluene and indicated that the introduction of CTAB facilitated the complete oxidation of by-products into CO₂ and H₂O. Full article

(This article belongs to the Special Issue Environmental Catalysis and Air Pollution Control)

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14 pages, 3872 KiB

Open AccessArticle

Catalytic Oxidation of NO by Ozone over Mn-Ce/Al₂O₃/TiO₂ Catalyst

by Hong Shen, Zijun Tang, Xiang Xiao, Haiwen Wu, Hang Zhou, Ping Fang, Dingfang Zhu and Jianhua Ge

Processes 2022, 10(10), 1946; https://doi.org/10.3390/pr10101946 - 27 Sep 2022

Cited by 4 | Viewed by 1279

Abstract

In this study, Mn-Ce/Al₂O₃/TiO₂ catalyst prepared by impregnation method was used for synergistic O₃ oxidation NO. The catalyst prepared by impregnating Al₂O₃/TiO₂ at a Mn:Ce molar ratio of 4:1 showed the best [...] Read more.

In this study, Mn-Ce/Al₂O₃/TiO₂ catalyst prepared by impregnation method was used for synergistic O₃ oxidation NO. The catalyst prepared by impregnating Al₂O₃/TiO₂ at a Mn:Ce molar ratio of 4:1 showed the best catalytic activity. The catalyst performance showed that when the molar ratio of Mn:Ce was 4:1 and the volume ratio of O₃:NO was 1:4, the removal rate of NO could reach 63%, which could increase the removal rate by 40% compared with that of NO oxidized by O₃ alone. BET, XRD, and TEM characterization results showed that when the molar ratio of Mn:Ce was 4:1, the catalyst specific surface area, and pore capacity were the largest. A large amount of MnOx and CeOx were distributed on the catalyst surface. The XPS analysis showed that the oxidation-reduction and oxygen vacancy of Mn (IV)/Mn (III)/Mn (II) and Ce (IV)/Ce (III), had a synergistic effect on the decomposition of O₃ into reactive oxygen species(O*), thus improving the catalytic capacity of Mn-Ce/Al₂O₃/TiO₂ catalyst for O₃. The O₂-TPD analysis showed that the oxygen vacancies and oxygen species in the catalyst could be used as the active point of decomposition of O₃ into O*. The experimental results show that the prepared catalyst can significantly improve the efficiency of ozone oxidation of NO and reduce the amount of ozone. The catalyst can be applied to ozone oxidation denitrification technology. Full article

(This article belongs to the Special Issue Environmental Catalysis and Air Pollution Control)

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13 pages, 2850 KiB

Open AccessArticle

Deactivation of Pd/SSZ-13 by Potassium and Water for Passive NO_x Adsorption

by Chi Fan, Jinxing Mi, Qin Wu, Jianjun Chen and Junhua Li

Processes 2022, 10(2), 222; https://doi.org/10.3390/pr10020222 - 25 Jan 2022

Cited by 6 | Viewed by 2067

Abstract

The passive NO_x adsorber (PNA) material has been considered an effective candidate for the control of NO_x from diesel exhaust during the engine cold start stage, and Pd/SSZ-13 attracts peoples’ attention mainly due to its superior hydrothermal stability and sulfur resistance. [...] Read more.

The passive NO_x adsorber (PNA) material has been considered an effective candidate for the control of NO_x from diesel exhaust during the engine cold start stage, and Pd/SSZ-13 attracts peoples’ attention mainly due to its superior hydrothermal stability and sulfur resistance. However, chemical poisoning tolerance of Pd/SSZ-13 is another key parameter to its practical application and future development. Herein, we prepared potassium-loaded Pd/SSZ-13 and evaluated the influence on NO_x adsorption ability. The characterization results revealed that the loading of potassium could not destruct the structure of SSZ-13 but impaired the BET surface area and pore structure through the sintering of Pd species to PdO. Meanwhile, the grown PdO phase restrained the NO_x adsorption ability and promoted the generation of NO₂ at high temperatures. Moreover, the presence of H₂O could also impair the NO_x adsorption ability due to the competitive adsorption between H₂O and NO_x. This work verifies that the design of Pd/SSZ-13 sample with stable Pd species and excellent hydrophobicity is significant for its further application under harsh conditions. Full article

(This article belongs to the Special Issue Environmental Catalysis and Air Pollution Control)

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14 pages, 5312 KiB

Open AccessArticle

Highly Active CuO/KCC−1 Catalysts for Low-Temperature CO Oxidation

by Yiwei Luo, Yonglong Li, Conghui Wang, Jing Wang, Wenming Liu, Honggen Peng and Daishe Wu

Processes 2022, 10(1), 145; https://doi.org/10.3390/pr10010145 - 11 Jan 2022

Cited by 4 | Viewed by 1514

Abstract

Copper catalysts have been extensively studied for CO oxidation at low temperatures. Previous findings on the stability of such catalysts, on the other hand, revealed that they deactivated badly under extreme circumstances. Therefore, in this work, a series of KCC−1-supported copper oxide catalysts [...] Read more.

Copper catalysts have been extensively studied for CO oxidation at low temperatures. Previous findings on the stability of such catalysts, on the other hand, revealed that they deactivated badly under extreme circumstances. Therefore, in this work, a series of KCC−1-supported copper oxide catalysts were successfully prepared by impregnation method, of which 5% CuO/KCC−1 exhibited the best activity: CO could be completely converted at 120 °C. The 5% CuO/KCC−1 catalyst exhibited better thermal stability, which is mainly attributed to the large specific surface area of KCC−1 that facilitates the high dispersion of CuO species, and because the dendritic layered walls can lengthen the movement distances from particle-to-particle, thus helping to slow down the tendency of active components to sinter. In addition, the 5% CuO/KCC−1 has abundant mesoporous and surface active oxygen species, which are beneficial to the mass transfer and promote the adsorption of CO and the decomposition of Cu⁺–CO species, thus improving the CO oxidation performance of the catalyst. Full article

(This article belongs to the Special Issue Environmental Catalysis and Air Pollution Control)

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13 pages, 4104 KiB

Open AccessArticle

Preparation of K Modified Three-Dimensionally Ordered Macroporous MnCeO_x/Ti_0.7Si_0.3O₂ Catalysts and Their Catalytic Performance for Soot Combustion

by Chunlei Zhang, Di Yu, Chao Peng, Lanyi Wang, Xiaoqiang Fan, Xuehua Yu and Zhen Zhao

Processes 2021, 9(7), 1149; https://doi.org/10.3390/pr9071149 - 30 Jun 2021

Cited by 5 | Viewed by 1741

Abstract

Soot particles in diesel engine exhaust is one of the main reasons for hazy weather and elimination of them is urgent for environmental protection. At present, it is still a challenge to develop new catalysts with high efficiency and low cost. In this [...] Read more.

Soot particles in diesel engine exhaust is one of the main reasons for hazy weather and elimination of them is urgent for environmental protection. At present, it is still a challenge to develop new catalysts with high efficiency and low cost. In this paper, a kind of K modified three-dimensionally ordered macroporous (3DOM) MnCeO_x/Ti_0.7Si_0.3O₂ catalysts are designed and synthesized by a sample method. Due to the macroporous structure and synergistic effect of K, Mn, and Ce, the K_nMnCeO_x/Ti_0.7Si_0.3O₂ (K_nMnCeO_x/M-TSO) catalysts exhibit good catalytic performance for soot combustion. The catalytic activity of K_0.5MnCeO_x/M-TSO was the best, and the T₁₀, T₅₀, and T₉₀ are 287, 336, and 367 °C, respectively. After the prepared catalyst was doped with K, the physicochemical properties and catalytic performance changed significantly. In addition, the K_0.5MnCeO_x/M-TSO catalyst also somewhat exhibits sulfur tolerance owing to it containing Ti. Because of its simple synthesis, high activity, and low cost, the prepared K_nMnCeO_x/M-TSO catalysts are regarded as a promising candidate for application. Full article

(This article belongs to the Special Issue Environmental Catalysis and Air Pollution Control)

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7 pages, 1107 KiB

Open AccessArticle

High Temperature Adsorption of SO₂ on Mixed Oxides Derived from CaAl Hydrotalcite-Like Compounds

by Hailin Wang, Run Hao, Meiping Gao, Zhongshen Zhang and Zhengping Hao

Processes 2021, 9(2), 325; https://doi.org/10.3390/pr9020325 - 10 Feb 2021

Cited by 5 | Viewed by 1879

Abstract

SO₂ which is usually emitted at high temperature is one of the most important air pollutants. It is of great significance to develop high temperature SO₂ adsorbent with high efficiency and low cost. In this work, a series of hydrotalcite-like compound-derived [...] Read more.

SO₂ which is usually emitted at high temperature is one of the most important air pollutants. It is of great significance to develop high temperature SO₂ adsorbent with high efficiency and low cost. In this work, a series of hydrotalcite-like compound-derived CaAlO and CaXAlO(X = Ce, Co) were prepared by coprecipitation and calcination method, and were employed as adsorbents for SO₂ adsorption at high temperature (700 °C). The structure and surface properties of these adsorbents were characterized by XRD, Brunauer–Emmett–Teller (BET), Derivative thermogravimetric analysis (DTG) and CO₂-TPD (temperature programmed desorption) measurement. Addition of a minor amount of Ce, Co (5 wt%) could significantly increase the number of weak alkalinity sites. CaO in CaCeAlO showed the best SO₂ adsorption capacity of 1.34 g/g, which is two times higher than that of CaO in CaAlO (0.58 g/g). Full article

(This article belongs to the Special Issue Environmental Catalysis and Air Pollution Control)

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13 pages, 2332 KiB

Open AccessArticle

Bimetallic Pt-Co Nanoparticle Deposited on Alumina for Simultaneous CO and Toluene Oxidation in the Presence of Moisture

by Peng Peng, Jun Li, Shengpeng Mo, Qi Zhang, Taiming Shen and Qinglin Xie

Processes 2021, 9(2), 230; https://doi.org/10.3390/pr9020230 - 26 Jan 2021

Cited by 9 | Viewed by 2105

Abstract

Carbon monoxide (CO) and hydrocarbons (HCs) generally have competitive adsorption on the active site of noble-metal nano-catalysts, thus developing an effective way to reduce the passivation of competitive reaction with each other is an urgent problem. In this study, we successfully synthesized transition [...] Read more.

Carbon monoxide (CO) and hydrocarbons (HCs) generally have competitive adsorption on the active site of noble-metal nano-catalysts, thus developing an effective way to reduce the passivation of competitive reaction with each other is an urgent problem. In this study, we successfully synthesized transition metal-noble metal (Pt-M) alloys via introducing inexpensive metal elements (M = Ni, Co and Cu) into Pt particles and then deposited on alumina support to form Pt-based catalysts. Subsequently, we choose CO and toluene as polluting gases to evaluate the catalytic activities of Pt-M/Al₂O₃ catalysts. Introducing inexpensive metal elements (M = Ni, Co, and Cu) significantly changed the physicochemical properties and catalytic activities of these Pt-based catalysts. It can be found that the Pt-Co/Al₂O₃ catalyst exhibited outstanding catalytic activity for CO and toluene oxidation under mixed gas atmosphere, compared with other Pt-based catalysts, which is due to the higher dispersity, more surface adsorption oxygen, and well redox ability. Surprisingly, H₂O could promote the catalytic activities for CO/toluene co-oxidation over the Pt-Co/Al₂O₃ catalyst. Thus, the present synthetic strategy not only opens an avenue towards the synthesis of noble metal-based catalysts, but also provides an excellent tolerance to H₂O in the catalytic process. Full article

(This article belongs to the Special Issue Environmental Catalysis and Air Pollution Control)

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21 pages, 5314 KiB

Open AccessArticle

Chlorine-Resistant Hollow Nanosphere-Like VO_x/CeO₂ Catalysts for Highly Selective and Stable Destruction of 1,2-Dichloroethane: Byproduct Inhibition and Reaction Mechanism

by Yu Huang, Shiyue Fang, Mingjiao Tian, Zeyu Jiang, Yani Wu and Chi He

Processes 2021, 9(1), 119; https://doi.org/10.3390/pr9010119 - 07 Jan 2021

Cited by 7 | Viewed by 2046

Abstract

Developing economical and robust catalysts for the highly selective and stable destruction of chlorinated volatile organic compounds (CVOCs) is a great challenge. Here, hollow nanosphere-like VO_x/CeO₂ catalysts with different V/Ce molar ratios were fabricated and adopted for the destruction of1,2–dichloroethane [...] Read more.

Developing economical and robust catalysts for the highly selective and stable destruction of chlorinated volatile organic compounds (CVOCs) is a great challenge. Here, hollow nanosphere-like VO_x/CeO₂ catalysts with different V/Ce molar ratios were fabricated and adopted for the destruction of1,2–dichloroethane (1,2–DCE). The V_0.05Ce catalyst possessed superior catalytic activity, reaction selectivity, and chlorine resistance owing to a large number of oxygen vacancies, excellent low-temperature redox ability, and chemically adsorbed oxygen (O⁻ and O₂⁻) species mobility. Typical chlorinated byproducts (CHCl₃, CCl₄, C₂HCl_3, and C₂H₃Cl₃) derived from the cleavage of C–Cl and C–C bonds of 1,2–DCE were detected, which could be effectively inhibited by the abundant acid sites and the strong interactions of VO_x species with CeO₂. The presence of water vapor benefited the activation and deep destruction of 1,2–DCE over V_0.05Ce owing to the efficient removal of Cl species from the catalyst surface. Full article

(This article belongs to the Special Issue Environmental Catalysis and Air Pollution Control)

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20 pages, 1363 KiB

Open AccessReview

Application of Stable Isotope Techniques in Tracing the Sources of Atmospheric NO_X and Nitrate

by Shaosong Zhen, Min Luo, Yang Shao, Diandou Xu and Lingling Ma

Processes 2022, 10(12), 2549; https://doi.org/10.3390/pr10122549 - 30 Nov 2022

Cited by 2 | Viewed by 1502

Abstract

Nitrate is an important component of PM_2.5, and its dry deposition and wet deposition can have an impact on ecosystems. Nitrate in the atmosphere is mainly transformed by nitrogen oxides (NO_X = NO + NO₂) through a number [...] Read more.

Nitrate is an important component of PM_2.5, and its dry deposition and wet deposition can have an impact on ecosystems. Nitrate in the atmosphere is mainly transformed by nitrogen oxides (NO_X = NO + NO₂) through a number of photochemical processes. For effective management of the atmosphere’s environment, it is crucial to understand the sources of atmospheric NO_X and the processes that produce atmospheric nitrate. The stable isotope method is an effective analytical method for exploring the sources of NO₃⁻ in the atmosphere. This study discusses the range and causes of δ¹⁵N data from various sources of NO_X emissions, provides the concepts of stable isotope techniques applied to NO_X traceability, and introduces the use of Bayesian mixture models for the investigation of NO_X sources. The combined application of δ¹⁵N and δ¹⁸O to determine the pathways of nitrate formation is summarized, and the contribution of Δ¹⁷O to the atmospheric nitrate formation pathway and the progress of combining Δ¹⁷O simulations to reveal the atmospheric oxidation characteristics of different regions are discussed, respectively. This paper highlights the application results and development trend of stable isotope techniques in nitrate traceability, discusses the advantages and disadvantages of stable isotope techniques in atmospheric NO_X traceability, and looks forward to its future application in atmospheric nitrate pollution. The research results could provide data support for regional air pollution control measures. Full article

(This article belongs to the Special Issue Environmental Catalysis and Air Pollution Control)

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